66 



Symposium on Microseisms 



Discussion 



Carl F. Romney 

 Geotechnical Corporation at Troy 



Microseismic motions over a wide range 

 of periods have been detected and reported in 

 the literature; however, quantitative informa- 

 tion on the ground amplitudes associated with 

 the various periods is surprisingly difficult to 

 find. Further, measurements describing the 

 spectrum existing at a given locality and time 

 are generally found to include only a narrow 

 band of periods, usually of about one octave 

 band width selected by the filter characteris- 

 tics of conventional observatory seismographs. 

 Most of the known information deals with the 



same "storm microseisms" discussed by Dr. 

 Bath's paper, which is chiefly concerned with 

 periods in the range 4-8 seconds. The spectra 

 to be presented here cover a much wider band 

 width, extending over nearly four octaves. 

 Such data describe more completely the state 

 of earth activity during a given meteorological 

 situation, and in addition, variations in spectra 

 due to location and time provide some insight 

 into the problem of extinction of short period 

 microseisms, which is studied by Dr. Bath. 



During August of 1950, identical horizon- 

 tal seismographs were operated at the Harvard 

 College Observatory, Harvard, Massachusetts, 

 and at the Rensselaer Polytechnic Institute's 

 Pinewoods Observatory, near Troy, New York, 



